With the recent advent of an advanced information society, an amount of data treated by computers has been increasing, and there has been a growing trend of collective management of many computers disposed in the same room in a facility such as a data center. For example, in such a data center, many racks (server racks) are disposed in a computer room and a plurality of computers (servers) are housed in each of the racks. Moreover, a large volume of jobs are efficiently processed by being organically distributed to the computers depending on operational states of the computers.
Meanwhile, each computer generates a large amount of heat during operation. A rise in temperature inside the computer may cause a malfunction or a failure. Accordingly, cooling air is taken into each rack by using a cooling fan, and the heat generated inside the computer is discharged to the outside of the rack.
In the meantime, the data center consumes a lot of electric power and there is a demand for reducing power consumption from the viewpoint of energy conservation. In order to prevent failures or malfunctions of the computers due to the heat, a conceivable solution is to constantly rotate cooling fans each at the maximum number of revolutions. Nevertheless, there are many cooling fans disposed in the data center. If such many cooling fans are constantly rotated each at the maximum number of revolutions, the power consumption is increased and the reduction in power consumption is therefore unachievable.
Hence, in order to reduce the power consumption in the facility such as the data center, it is important to efficiently operate cooling equipment in accordance with the operational states of the computers.    Patent Document 1: Japanese Laid-open Patent Publication No. 2008-227127    Patent Document 2: Japanese Laid-open Patent Publication No. 2011-222029    Non-patent Document 1: ASTROM, K., and HAGGLUND, T.: “PID controllers: theory, design and tuning” (ISA Press, Research Triangle Park, N.C., 1995)